1. Field of the Invention
The present invention relates to a communication apparatus and program for interference detection and signal transmission methods.
2. Description of the Related Art
As a conventional system for performing interference measurement and signal transmission, there is a system that coexists with another system using the same frequency as the former. In this system, it is determined, using an interfering signal-level determination circuit, whether there exists an interfering signal, and if the level of a received interfering signal exceeds a threshold value, signal transmission is interrupted for a preset time and then resumed (see, for example, JP-A 2001-333081 (KOKAI)).
In the prior art, no problem will occur when a plurality of systems utilizing a narrow-band time-division scheme coexist. However, when systems utilizing a wide-band frequency-division scheme coexist, if interference detection is performed for only a short time, detailed features of interference cannot be detected, and hence communication of signals made to be orthogonal to interfering signals cannot be executed. As a result, communication may be interrupted.
Further, the system throughput may be significantly reduced because of the influence of unlicensed systems existing in the same frequency band. In addition, to detect detailed features of interference, much time is required, which results in reduction of the system throughput.